Drawing of filament bundles in the form of a curtain, suitable apparatus therefor, and use thereof for producing spunbonded webs.
The present invention relates to a process for drawing filament bundles, to an apparatus especially adapted therefor, and to the use thereof in the production of spunbonded webs.
The drawing of filament bundles by means of drawing nozzles is known per se. For instance, in the production of spunbonded webs, molten polymer is spun through spinnerets, drawn by means of drawing nozzles through air friction and then laid down on a conveyor belt to form a web. This web is subsequently consolidated and transported out of the plant. Examples of said processes are described in Vliesstoffe, eds. J. L unenschlob and W. Albrecht, G. Thieme Verlag 1982, pp. 106-108.
It has also already been proposed to produce spunbonded webs by the curtain spinning process. In the curtain spinning process, the spinnerets are arranged in series, so that the filaments are spun in the form of a curtain. The patent literature already contains several proposals for carrying out the curtain spinning process, for example DE-B-2,048,006, DE-C-3,117,737, DE-A-3,701,531, DE-A-3,713,861 and DE-A-3,401,639.
Furthermore, DE-A-1,785,158 discloses a nozzle with adjoining filament duct, which is used especially in the production of non-woven products from laid-down continuous filaments. Embodiments are described of these nozzles which can be used in curtain spinning. However, such constructions have hitherto not been used in practice. One of the reasons for this is the hitherto inadequate control of the uniformity of the drawing conditions.
It has further also already been proposed to make drawing nozzle shaft walls deformable in order that different drawing conditions may be established in this way. DE-A-3,503,818 describes such an apparatus wherein the drawing shaft walls consist of a deformable material which in operation allows a deformation of the drawing shaft walls in the manner of a Venturi nozzle and which are deformable in a predetermined manner by means of adjusting drives. In said previously known nozzle, the entire draw takes place within a relatively confined region in the Venturi nozzle.